Re: [PATCH v3] vfio/pci: Fix integer overflows, bitmask check

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 12 Oct 2016 18:51:24 +0200
Vlad Tsyrklevich <vlad@tsyrklevich.net> wrote:

> The VFIO_DEVICE_SET_IRQS ioctl did not sufficiently sanitize
> user-supplied integers, potentially allowing memory corruption. This
> patch adds appropriate integer overflow checks, checks the range bounds
> for VFIO_IRQ_SET_DATA_NONE, and also verifies that only single element
> in the VFIO_IRQ_SET_DATA_TYPE_MASK bitmask is set.
> VFIO_IRQ_SET_ACTION_TYPE_MASK is already correctly checked later in
> vfio_pci_set_irqs_ioctl().
> 
> Furthermore, a kzalloc is changed to a kcalloc because the use of a
> kzalloc with an integer multiplication allowed an integer overflow
> condition to be reached without this patch. kcalloc checks for overflow
> and should prevent a similar occurrence.
> 
> Signed-off-by: Vlad Tsyrklevich <vlad@tsyrklevich.net>
> ---
>  drivers/vfio/pci/vfio_pci.c       | 33 +++++++++++++++++++++------------
>  drivers/vfio/pci/vfio_pci_intrs.c |  2 +-
>  2 files changed, 22 insertions(+), 13 deletions(-)

I've applied this to my for-linus branch for v4.9, thanks,

Alex
 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index d624a52..031bc08 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -829,8 +829,9 @@ static long vfio_pci_ioctl(void *device_data,
>  
>  	} else if (cmd == VFIO_DEVICE_SET_IRQS) {
>  		struct vfio_irq_set hdr;
> +		size_t size;
>  		u8 *data = NULL;
> -		int ret = 0;
> +		int max, ret = 0;
>  
>  		minsz = offsetofend(struct vfio_irq_set, count);
>  
> @@ -838,23 +839,31 @@ static long vfio_pci_ioctl(void *device_data,
>  			return -EFAULT;
>  
>  		if (hdr.argsz < minsz || hdr.index >= VFIO_PCI_NUM_IRQS ||
> +		    hdr.count >= (U32_MAX - hdr.start) ||
>  		    hdr.flags & ~(VFIO_IRQ_SET_DATA_TYPE_MASK |
>  				  VFIO_IRQ_SET_ACTION_TYPE_MASK))
>  			return -EINVAL;
>  
> -		if (!(hdr.flags & VFIO_IRQ_SET_DATA_NONE)) {
> -			size_t size;
> -			int max = vfio_pci_get_irq_count(vdev, hdr.index);
> +		max = vfio_pci_get_irq_count(vdev, hdr.index);
> +		if (hdr.start >= max || hdr.start + hdr.count > max)
> +			return -EINVAL;
>  
> -			if (hdr.flags & VFIO_IRQ_SET_DATA_BOOL)
> -				size = sizeof(uint8_t);
> -			else if (hdr.flags & VFIO_IRQ_SET_DATA_EVENTFD)
> -				size = sizeof(int32_t);
> -			else
> -				return -EINVAL;
> +		switch (hdr.flags & VFIO_IRQ_SET_DATA_TYPE_MASK) {
> +		case VFIO_IRQ_SET_DATA_NONE:
> +			size = 0;
> +			break;
> +		case VFIO_IRQ_SET_DATA_BOOL:
> +			size = sizeof(uint8_t);
> +			break;
> +		case VFIO_IRQ_SET_DATA_EVENTFD:
> +			size = sizeof(int32_t);
> +			break;
> +		default:
> +			return -EINVAL;
> +		}
>  
> -			if (hdr.argsz - minsz < hdr.count * size ||
> -			    hdr.start >= max || hdr.start + hdr.count > max)
> +		if (size) {
> +			if (hdr.argsz - minsz < hdr.count * size)
>  				return -EINVAL;
>  
>  			data = memdup_user((void __user *)(arg + minsz),
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index c2e6089..1c46045 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -256,7 +256,7 @@ static int vfio_msi_enable(struct vfio_pci_device *vdev, int nvec, bool msix)
>  	if (!is_irq_none(vdev))
>  		return -EINVAL;
>  
> -	vdev->ctx = kzalloc(nvec * sizeof(struct vfio_pci_irq_ctx), GFP_KERNEL);
> +	vdev->ctx = kcalloc(nvec, sizeof(struct vfio_pci_irq_ctx), GFP_KERNEL);
>  	if (!vdev->ctx)
>  		return -ENOMEM;
>